Amino-polysaccharides and copolymers thereof for contact lenses and ophthalmic compositions

ABSTRACT

Aminopolysaccharides and copolymers thereof, primarily those of N-acetyl-D-glucosamines and derivatives and various monomers, is described.

BACKGROUND OF THE INVENTION

This invention relates to the use of a polysaccharide known as chitin,as well as other derivatives of chitin, and copolymers of the family ofmaterials known as amino-polysaccharides useful for making contactlenses or parts thereof, artificial corneas and interocular lens types,drug delivery systems, vaginal spermicides and creams, injectableencapsulation materials and other medical devices and pharmaceuticals.These amino-polysaccharides are used alone or as components in apolymeric arrangement, such as polymer blends, graft or blockcopolymers, or any other combination of modified compositions.

Chitin is an amino sugar, in which one or more of the hydroxyl groups ofthe carbohydrate are replaced by an amino group. Chitin is one of themost abundant amino sugar derivatives. The amino polysaccharide is madeup of 2-acetamido-2-deoxyglucose units linked in a B-1,4 manner similarto that in cellulose, or starch, or in general it is indicated asN-acetyl-D-gluocosamine, and is found as a structural material in theinvertebrate animal world. The exoskeletons of insects and crustaceanscontain large amounts of this amino polysaccharide. The observation ofthe exoskeleton of shrimp and other invertebrates indicates that thismaterial can be made clear, flexible, hard, and permeable, which wouldbe useful for medical devices.

Chitin has been estimated to be the second most abundant polysaccharidein nature with synthesis in the neighborhood of a billion tons a year.However, in the natural state it occurs in small flakes or as shortfibrous materials, and is not capable of forming useful shaped articleswithout solution and reprecipitation or renaturing. Methods ofdissolving chitin in certain solvents are described in the literature.For example, Clarke and Smith, J. Phys. Chem., 40, 863 (1936), useaqueous acids or lithium salts for solution and regeneration of chitin.These authors observed the formation of addition compounds of chitinwith lithium thiocyanate and with sodium hydroxide under certainconditions. However, the formation of addition compounds or complexes ofchitin with organic compounds has not been described.

The N-acetyl-D-glucosamine can be prepared in 60 to 70% yields by thehydrolysis of the exoskeleton of crustaceans with concentratedhydrochloric acid; ##STR1##

Poly(N-acetyl-D-glucosamine) is a major component of naturally occurringchitin. The naturally occurring material has not only thepoly(N-acetyl-D-glucosamine) but also inorganic salts thought to beforms of calcium carbonate and proteinaceous materials, the compositionof which is not presently known. The term N-acetyl-D-glucosamine is usedherein to refer to the various naturally occurring forms of chitinincluding the purified and or naturally occurring form. A method ofextracting the N-acetyl-D-glucosamine is the following: chitin is finelyground in a ball mill overnight or until it passes a 6 mm screen and canbe retained by a 1 mm screen. 149 g of this finely ground material isdecalcified by extracting with 825 ml of 2 N HCl at 4° C. for 48 hoursin a flask stirred with a magnetic stirrer. The material is collected bycentrifugation and washed repeatedly with water until neutral. The ashcontent is about 0.4-0.5%. The decalcified chitin is then stirred atroom temperature with 1500 ml of 90% formic acid overnight. The mixtureis centrifuged and the residue repeatedly washed with water. The washedchitin is then suspended in 2 liters of 10% NaOH solution and heated at90°-100° C. for 2.5 hours. The solution is filtered, and washed withwater until neutral, washed several times with absolute ethanol andether, and dried at 40° C. under reduced pressure to yieldpoly(N-acetyl-D-glucosamine).

PRIOR ART

Carboxymethylchitin is disclosed in Carbohyd. Res. 7, 483-485 (1968), R.Trujillo. This article mentions the hydrolysis of both chitin andcarboxymethylchitin by lysozyme.

U.S. Pat. No. 3,632,754 teaches the application of a powder or solutionof chitin or chitin derivative to accelerate the rate of wound healingin mammals.

U.S. Pat. No. 4,063,016 teaches compositions of chitin with lowermolecular weight alcohols, aldehydes and ketones.

U.S. Pat. No. 3,892,731 teaches the use of di-or-tri- chloroacetic acidas a solvent for chitin.

U.S. Pat. No. 4,027,068 describes a method of using chitin derivativesas defoggers for clear surfaces and as deodorizers.

U.S. Pat. No. 3,988,411 teaches that poly(N-acetyl-D-glucosamine) issoluble in hexafluoroisopropyl alcohol and hexafluoroacetonesesquihydrate.

U.S. Pat. No. 3,847,897 teaches how to prepare microcrystalline chitinby subjecting chitin to controlled acid hydrolysis and high shear whilesuspended in aqueous medium.

SUMMARY OF THE INVENTION

It is the essence of this invention to utilize the unique properties ofN-acetyl-glucosamine, substituted D-glucosamine, and copolymers ofD-glucosamine, in an area of application which can take advantage of theproperties of these materials, that being the ophthalmic field ofcontact lenses, ophthalmic drug preparations, contact lens solutions,etc.

It is interesting to note other structural amino polysaccharides whichcan be used in this invention. Hyaluronic acid is an aminopolysaccharide of 2-amino-2-deoxyglucose and glucuronic acid. Thispolymer polysaccharide is an important component of animal connectivetissue and of the synovial fluid which is the natural lubricant ofjoints. 2-amino-deoxygalactose, is also an important naturally occurringamino acid known for many years as a component of the polysaccharidechondroitin sulfate. This polymer is among the principal polysaccharidesof cartilage and is structurally similar to hyaluronic acid, except thatthe amino sugar is galactose instead of glucose and a sulfate group isalso present. The reactions with N-acetyl-D-glucosamine and the aboveamino polysaccharides are similar, and with slight modifications of themethods can be substituted for N-acetyl-D-glucosamine.

There are similarities between the amino-polysaccharides, and starch andcellulose. All have hydroxyl groups which may be esterified by inorganicor organic acids to modify their properties. The literature shows theformation of a complex of chitin with an oxygen-containing complexingagent containing up to 10 carbon atoms selected from the groupconsisting of saturated aliphatic and alicyclic alcohols, aldehydes, andketones. It is possible to prepare derivatives which have more than onetype of substituent on the chitin chain. Derivatives of chitin can beformed by attaching a substituent to the 6-hydroxyl oxygen or byremoving the N-acetyl group to form chitosan, and attaching anothersubstituent to the nitrogen. Chitosan itself is commercially available,and is thus a useful starting material for the preparation of chitinderivatives in which a substituent is attached to the nitrogen. Thecarboxy-containing chitin derivatives which are useful are theO-carboxy-alkyl chitin, in which a carboxy alkyl group is attached tothe 6-hydroxyl oxygen through the alkyl group; N-carboxyalkyl chitosansin which a carboxyalkyl group is attached to the nitrogen through thealkyl group, and N-carboxyacyl chitosan in which the nitrogen isacylated with material containing a carboxyl group in addition to theacyl group which is attached to the nitrogen. Substituents need not belimited to one type of substituent on the chitin chain. These othersubstituents need not be limited to carboxy containing substituents, andin fact, alkyl and substituted alkyl substituents having 2-18 C-atomsare often used because they can modify the solubility of the chitinderivatives.

Some of the substituted N-acetyl-D-glucosamines can be used in anenzymatically degradable form by the selection of specific substituents.Examples of these are poly(M-acetyl-6-O-(carboxymethyl)-D-glucosamine),poly(N-acetyl-6-O-(2-hydroxyethyl)-D-glucosamine) and poly(N-acetyl-6-O-(ethyl)-D-glucosamine).

To form poly(N-acetyl-6-O-(2-hydroxyethyl)-D-glucosamine), 13.6 g ofpurified poly (N-acetyl-D-glucosamine) milled so that it passes a 1 mmsieve are placed in a screw-cap bottle. Then 200 ml of cold (0°-5° C.)aqueous 43% NaOH are added and the contents stirred for two hours undernitrogen and then hold at 0°-4° C. for 10 hours. The swollen alkaliderivative is then squeezed to 3 times its original weight in a sinteredglass funnel, disintegrated and frozen at -20° C. under nitrogen for onehour and then thawed at room temperature for one hour. The freeze/thawcycle is repeated 3 times. To the alkali derivative are added 120 ml ofdimethyl sulfoxide and the slurry is immediately stirred and autoclayed.The autoclave is purged several times with nitrogen and 53.2 ml ofethylene oxide are added. The mixture is held at 50° C. for 18 hours.The solution is carefully neutralized with glacial acetic acid. Thealkyl-substituted N-acetyl-D-glucosamine can be crosslinked by formingan aqueous solution with acetone and using an olefin glycoldimethacrylate such as ethylene glycol dimethacrylate, etc. This willadd to the tensile strength of the film formed.

The ability to modify chitin by substituents, allows for the material tobe substituted, or compounded, using bio-organic compounds which canmodify its properties for use in medical devices. Some of thebio-organic compounds which can be added by substitution, block andgrafting, or polyblending, are collagen, which has a composition inwhich one-third of the amino acid residues are glycine; elastin andresilin may also be used. Resilin is insoluble in the usual solvents andin solutions of urea, these can reduce the enzymatic reaction of thebody on some of the compounds of N-acetyl-D-glucosamine, and canregulate the biodegradability of the material in certain uses.

To prepare a collagen derivative of chitin, or chitosan, 3.44 gms in asolution, which yield 4% chitosan, in 2% acetic acid (vacuum filtered),3.44 gms of 8% Crotein SPC in 2% acetic acid, and 0.033 of 0.593%glutaraldehyde. The mixture is heated at 60° for about 4 hours toencourage interaction. The solution is evaporated by heating to 100° C.for approximately 4 hours. The residual product is evaporated and driedat 80° C. The materials are hard and brittle, but become pliable aftersoaking in water. The D-glucosamine-collagen complex forms a clearpolymer which can be used internally as an enzymatic degradable drugdelivery system, vaginal cream and spermicide, etc.

For the following discussion the term D-glucosamine will be used forN-acetyl-D-glucosamine, poly(N-acetyl-D-glucosamine), and any of itsderivatives, or substituted derivatives.

To alter the physical properties of the D-glucosamine, it may be graftor block copolymerized with known polymers to alter its chemicalstructure. In order to form graft or block copolymers with D-glucosamineit will be necessary to form free radicals. In free radical-initiatedgraft copolymerization, a free radical produced on the D-glucosaminereacts with a monomer to form graft copolymers. A number of initiatingmethods are used to prepare graft copolymers, initiation by chemicalmethods and initiation by irradiation. The method of choice depends onthe monomer to be copolymerized, the substitution on the D-glucosamineetc. a little thought will determine the appropriate procedure; it isthe final copolymers which have the desired biomedical use and not thespecific pathway to achieve them. The copolymer graft composition ofthis invention beside the biopolymers, consist essentially of theD-glucosamine units of the indicated reaction formulae, and anyacrylonitrile, acrylamide, alkyl methacrylate. The acetate, propionate,and butyrate esters of the D-glucosamine-g-poly(ethyl acrylate) andD-glucosamine-g-poly(butyl acrylate) copolymers can readily be formed.This graft polymerization reaction can be performed either in solution,emulsion or suspension. A part or whole of the redox catalyst in thereaction mixture may be replaced by a peroxide catalyst or a diazocompound catalyst. Free radicals have been formed on polyglucoses bychain transfer reactions. A frequently used method is the reaction of apolysaccharide with hydrogen peroxide in the presence of a ferrous salt,such as ferrous ammonium sulphate. Hydroxyl radicals are produced fromthe hydrogen peroxide-ferrous ion system, and these free radicals thenabstract hydrogen atoms from the polysaccharide. Hydrogen peroxide hasbeen replaced by organic hydroperoxides or inorganic persulfate salts,and such reducing agents as sodium bisulphite have been substituted forferrous ion. Mixtures of ferrous ammonium sulphate and ascorbic acid canalso serve as the reducing portion of the redox system. The use of thecatalyst compounds, may be omitted, under certain conditions and thematerials heat polymerized under suspending or emulsifying conditions.Or the use of catalyst compounds may be omitted, and ozone introducedinto an aqueous solution of D-glucosamine, after which the reactionsystem is heated and the oxidized D-glucosamine is graft polymerizedwith either an alkyl methacrylate, acrylonitrile, or an acrylamide undersuspending or emulsifying conditions. Where graft polymerization iscarried out using a redox catalyst, a solution polymerization may beemployed using a solvent which can dissolve both the D-glucosamine andthe copolymer, or a combination of solvents can be used. The materialsmay be polymerized in emulsion in the presence of a basic, neutral oracidic surface active agent in an aqueous medium. Or it can bepolymerized in suspension by omitting the use of a surfactant. Thepresence of molecular oxygen reduces the activity of the redox catalystand therefore, the reaction should be carried out after purging theliquid reaction medium and reaction zone with nitrogen. Furthermore, acompound capable of forming the copolymer compounds under acidicconditions during the polymerization reaction, such as cerium hydroxide,can be used.

The following is a method of initiating free radicals on theD-glucosamine. The method involves the use of ceric salts, such as cericammonium nitrate dissolved in nitric acid. The method is used to graftcopolymerize a number of monomers onto both starch and cellulosepolysaccharides. Based on available information the most likely reactionpath for ceric grafted copolymerization would appear to be: ##STR2##

After initial formation of a D-glucosamine ceric complex, ceric ion isreduced to cerous, a hydrogen atom is oxidized, and a free radical isformed on the D-glucosamine. The free radical D-glucosamine formed maythen react with monomer to initiate graft copolymers. The reaction withthe formed free radicals allows for the formation of the followingcompounds: D-glucosamine-acrylonitrile with varying degrees ofsubstitution of the acrylonitrile onto the D-glucosamine to vary thecharacteristics of the material. The formation of D-glucosamine andacrylamides, such as diacetone acrylamide, ethylacrylamide; N,Ndiethylacrylamide, etc. The acrylic acids and esters, and the modifiedacrylic acids and esters, as well as the methacrylates can be used.

The formation of copolymers of chitin and chitin derivatives withsilicones produces a class of copolymers which will find extensive usein biomedicine and bioengineering.

The basic structure of the silicones is exhibited bypolydimethylsiloxanes. A variety of groups can be substituted for themethyl group in a silicone, among some of the substitute groups are C₆H₅ -phenyl, CF₃ CH₂ CH₂ -trifluoropropyl, H-hydride which introducesmetal catalyzed and vinyl-addition cross-link sites, HO-silanol crosslinking points for condensation and metal-catalyzed cross-linking, CH₂═CH-vinyl increases peroxide reactivity, and introduces cross-linkpoints for vinyl addition.

Since some of the properties of the silicone homopolymers are nottotally compatable with biological use, the modifiedN-glucosamine-silicone will find increased biological use because of theunique wetting properties, hydrophilic nature, of the chitosan and otherN-glucosamine derivatives. These hydrophilic properties will impartsufficient wettability to the silicone to reduce tissue reaction withthese materials, which may be formed into implant devices, contactlenses, etc.

The chemistry of the silicones is well defined and bridge polymer linksbetween the silicone and chitin complexes are possible, as in thetransition between the siloxane to a carbinol-terminated (C--OH)polymer, which can be reacted with isocyanetes to form a urethanelinkage. Urethane linkage can be created by reacting silanol-terminatedpolymers with ethylene oxide to yield ethanol ether (SiOCH₂ CH₂ OH), byhydrating vinyl-terminated polymers (SiCH₂ CH₂ OH) and by adding allylalcohol to hydride terminated polymers (SiCH₂ CH₂ --CH₂ OH).

Several silicone materials have been tried for use in contact lensesbecause of the enhance oxygen permeability of the silicone, however, avariety of mechanical, optical, and wetting requirements posed aconsiderable problem to bioengineers. By copolymerizing the siliconewith a N-glucosamine many of the problems, and in particular thenon-wetting characteristics can be eliminated. This modifiedsilicone-N-glucosamine complex can find many uses in biomedicine besidescontact lenses, some of the uses are given in this disclosure, otherswill become possible by those skilled in the art.

Since extensive work has been done with the polysaccharide starch, andthe D-glucosamine is structurally similar to starch, the block and graftcopolymers possible with starch should be possible with D-glucosamine toproduce the diverse biocompatible polymers needed for the formation ofthe medical devices of the invention. Such graft or block copolymers canbe formed by olefinic compounds, both mono- and di-olefinic compounds,including acrylic acid and esters thereof with saturated alcohols,hydroxyalkyl methacrylate, alkylamino alkmethacrylate, olefin glycols,azo compounds; N-vinyl pyrrolidone, poly(N-vinylpyrrolidone), etc.Reactions covering these copolymers are given in the following forstarch: U.S. Pat. No. 3,414,530 shows graft copolymers of a polyalkyleneoxide on starch and dextrin polysaccharides. U.S. Pat. No. 3,332,897describes a process for preparing polysaccharide esters forsimultaneously polymerizing and grafting an ethylenically unsaturatedmonomer onto the polysaccharide, with an acylating agent selected fromacetic, propionic or butyric anhydrides or any combination thereof. U.S.Pat. No. 3,935,099 describes the copolymerization of starch andacrylonitrile. The reactions that are carried out with starch, andcellulose, can be carried out with D-glucosamine. By consulting theliterature the specific reaction can be found. This diverse family ofblock and graft copolymers of D-glucosamine and substitutedD-glucosamine provide a unique series of polymers for use in medicaldevices as well as other uses, such as pharmaceuticals and cosmetics,especially the collagen-D-glucosamine and silicone-D-glucosamine.

Another method which has been used successfully with cellulose, andsubstituted cellulose, e.g. ethyl cellulose, is block copolymerizationthrough mastication; this method may be found useful with theN-acetyl-D-glucosamine block copolymerization with acrylonitrile,acrylamides, and methacrylates. The polymers or polymer and monomer, aresubjected to a mechanical stress like that created by ball milling,mastication, or freezing and thawing of aqueous dispersions, thesegments resulting from these breaks are polymeric free radicals inwhich the free radical sites are located at the ends of the segmentswhere the breaks occurred. If this mechanical depolymerization iscarried out in the presence of a monomer, copolymerization is initiatedby macroradicals, and a block copolymer of poly(N-acetyl-D-glucosamine)may be produced by combinations of macroradicals.

The mastication technique works on monomers containing an olefin, ormulti-olefin bond, such as methacrylic acid and its esters, e.g., methylmethacrylate, ethyl methacrylate; vinyl acetate, acrylonitrile, allylacrylate, or acrylamides and various combinations of these. The methodsand procedure for polymerization using mechanical stress are known inthe art.

Polyblending whereby free radicals are generated by mechanical shearingis the easiest for the mixing, or grafting of the polymers and monomersdiscussed here. Free radicals are formed at the ruptured end of themolecules of the polymers, and are caused to initiate thecopolymerization of one or more polymerizable compounds, or monomers.The reaction can be aided by the addition of organic peroxides to thereaction mixture.

If the polymer is itself derived from an olefinic compound and themonomer mixed with it is of the same olefinic compound, the product is ahomopolymer. If, on the other hand, it is not the same, as in manyinstances in this invention, the product consists of a mixture ofhomopolymer and an interpolymer of the graft or block type in which thedifferent types of monomer molecules in their polymerized form aresegregated into separate segments of the molecule. These interpolymersare regarded as polymer compounds in which different homopolymericsegments are linked together chemically, i.e., copolymerized.

In order to produce polymeric materials by mechanical mixing of polymerand monomers, the mixture must not be in the form of a fluid solution ofthe polymer in the monomer, since adequate shearing to initiatepolymerization by rupturing polymer molecules cannot occur. Theconstituents of the polymer-monomer mixture and the relative proportionsshould be selected so that the mixture is somewhat rubbery at thetemperature of mastication, if mastication copolymerization is beingutilized.

Other factors which can be varied to assist in the production ofpolymer/monomer mixtures suitable for use in this invention includetemperature and the molecular weight of the polymer. The softeningeffect on the polymer of an increase in the temperature is sometimesuseful in assisting its conversion into a rubbery condition. The higherthe molecular weight of the polymer, the wider the range of proportionsof monomer or plasticizing solvent that result in the production of aproduct which can be mechanically transformed into a rubbery mixture. Itis understood that crosslinking agents and additional plasticizingagents will determine the final product.

The polymer/monomer mixture may be prepared by allowing the polymer toimbibe the monomer before mastication, this method being applicable togaseous as well as liquid monomers. Plasticizing solvents may beintroduced to aid mixing. It will be appreciated that if the monomer isa solid, e.g. acrylamide, it is necessary either to use a plasticizingsolvent in order to give the necessary degree of freedom, or to raisethe temperature at which the mixture is free, and can be masticated. Inany case it is often convenient to mix the polymer and monomer togetherwhen the polymer is in a molten or fluid state. The polymer-monomer orpolymer-monomer-plasticizing solvent mixture should preferably beconverted into the form of an homogeneous swollen mass beforepolymerization by mechanical means is initiated in order that a uniformpolymerization may be easily accomplished. This may be expedited bystirring or churning the mass in an open mixer and/or by raising thetemperature. Increase in temperature is useful with polymer-monomermixtures which gel at elevated temperature.

The series of polymers includes the following: D-glucosamine andacrylonitrile; D-glucosamine and an acrylamide; D-glucosamine and anacrylic acid or ester, D-glucosamine and a methacrylic acid or ester,D-glucosamine and a protein or polypeptide compound, D-glucosamine andcollagen; D-glucosamine and elastin and/or resilin; D-glucosamine and anazo compound, e.g. N-vinyl pyrrolidone; and the chemical familiesrepresented by the above compounds. These compounds produce a diversefamily of compounds, and whether the specific compound is graft or blockpolymerized through chain cleavage and free radical formation, orsubstituted on the side chain through the hydroxyl, or N-acetyl group,they are applicable to the following medical devices and uses:

A. Absorbable polymer alone

1. Solid products, molded or machined

a. Orthopedic pins, clamps, screws and plates

b. Clips (e.g. for use as hemostat)

c. Staples

d. Hooks, buttons and snaps

e. Bone substitute (e.g. mandible prosthesis)

f. Non-permanent intrauterine devices

g. Vascular implants or supports

h. Vertebral discs

i. Extracorporeal tubing for kidney and heart-lung machines

2. Fibrillar Products, knitted or woven, including velours

a. Burn dressings

b. Hernia patches

c. Absorbent paper or swabs

d. Medicated dressings

e. Facial Substitutes

f. Gauze, fabric-sheet, felt or sponge for liver hemostasis

g. Gauze bandages

h. Dental packs

i. Surgical sutures

3. Pharmaceuticals

a. Dental

b. Drug

c. Ophthalmic

Any other medical devices which can be used in the body, such as drugrelease devices, arterial graft or substitutes, bandages for the skinsurface, burn dressings (in combination possibly with other polymericfilms), two component systems, etc.

Contact lenses are well known in the art and have been used for manyyears. The lenses are made of several kinds of plastic; silicone rubberpoly(2-hydroxyethyl methacrylate), cellulose acetate butyrate, andpoly(methyl methacrylate). While these materials are opticallysatisfactory, their use has some disadvantages. Some are not gaspermeable, some will not wet properly, others, e.g., soft lenses, tendto tear easily, and some have low biocompatibility. Accordingly it wouldbe highly desirable to have a family of polymers to form contact lenseswhich are flexible, optically clear, water wettable, hydrophilic tovarious degrees, highly permeable to oxygen and carbon dioxide and whichin general exhibit a high degree of biocompatibility. The chitinproducts of this invention fulfill this requirement.

The main disadvantage of known soft of hydrophilic contact lenses isthat they have low tensile strength. The average life of a soft lenspresently on the market is from six months to one year, and with patientuse the lens tears easily. This invention provides materials formed fromcellulose or silicone graft copolymers which can have a high tensilestrength, thereby overcoming the present disadvantages of soft lenses.

The N-acetyl-D-glucosamine, the substituted and copolymers ofN-acetyl-D-glucosamine, all form materials which can be used for contactlenses. The substituted N-acetyl-D-glucosamine ofpoly(N-acetyl-6-0-carboxymethyl)-D-glucosamine, etc. and even chitin andchitosan 40/60, form clear films with high tensile strength and varyingdegrees of water absorption, I. Jaffe and H. R. Hepburn, "Observation onRegenerated Chitin Films", J. Material Science, 8(1973)1751-1754, givevalues on the strength of films of regenerated chitin, from a chitinxanthate dispersion, including a comparison of strength after 30 yearsstorage as 6.3×10³ pounds/sq inch.

Contact lenses are usually formed by casting, molding or lathe cuttingof plastic buttons. The D-glucosamine (chitin-chitosan 40/60chitosan-collagen, etc.) can be cast into a contact lens, by dissolvingit in a solvent and placing it either in a spin cast mold, or between amale and female die in a cavity, and allowing the solvent to evaporate,by any suitable means. To lathe cut the lenses, the D-glucosaminecompound composition is placed in a mold, or device to form it into asheet or rod form. The sheet is usually about 5/16 inch thick, the rodis formed into 1/2 inch diameter. The rod or sheet is then cut into whatis known in the trade as buttons, buttons are usually cylindrical inshape having dimensions of 1/2 inch diameter and 5/16 inch thickness.The buttons are mounted on radius cutting lathes, the concave surface isusually cut first, the radius is cut to a predetermined curvature, theradius is polished to remove all lathe marks on the lens. A polishingtool using commercial polishing agents, such as tin oxide, is used topolish the surface, other polishing agents used in the contact lensindustry as polishing agents may also be used. After the concave surfacehas been polished, the semi-finished lens is mounted into an outsidecutting lathe, the power radius, or convex, surface is now generated.The convex surface is then polished to remove all lathe marks. The lensis removed from the tool and cut to diameter, and the edge finished. Theside surfaces of the lens are subject to a bevel machine to produce acompleted lens.

The polymers which can be used to form contact lenses, and particular tosuch polymers is that they can be prepared with modifiers, plasticizers,and crosslinking agents, are those compositions of D-glucosaminementioned in this disclosure which are optically clear. It will also beevident that additional modification with N-acetyl-D-glucosamine will bepossible and will form contact lenses.

Because of the ability of N-acetyl-glucosamine to act as a wound-healingaccelerator, it can find an additional application for patients who haveundergone cataract surgery, or any other type of eye surgery toaccelerate the healing process. The N-acetyl-glucosamine should beformed into a soft lens material, or polyblended into the carrierpolymer to allow for maximum therapeutic effect, although any method isacceptable that will allow for the material to become functional. Sincethe eye after undergoing surgery is somewhat sensitive, it would be tothe patient's advantage to use a carrier which is soft,(chitin-collagen, etc.), or any soft lens material available.

The N-acetyl-glucosamine can be placed into solutions, and ointments foruse in the eye, and to act as wetting agents and viscosity builders incontact lens solutions. This will reduce the overwear syndromeexperienced with contact lenses. the N-acetyl-D-glucosamine compoundsproduce excellent viscosity builders and wetting agents for ophthalmicsolutions and contact lens solutions. The compositions act as both awetting agent and viscosity builder, among other things. The viscositybuilding characteristics, are used in the solution to provide cushioningand corneal comfort, while avoiding stickiness of the eyelid andgranulation on the eyelashes. These desirable properties can best beachieved through the use of D-glucosamines as the viscosity buildingagents and wetting agents, along with the other properties as part ofthe chemistry of the D-glucosamine compounds.

The use of the polymers of this invention also constitutes a novelcomposition for use in ophthalmic compositions and preparations. Thecompositions act as both a wetting agent and viscosity builder, amongother things. The viscosity building characteristics are used in thesolution to provide cushioning and corneal comfort, while avoidingstickiness of the eyelid and granulation on the eyelashes. Thesedesirable properties can best be achieved through the use of thepolymers described in this invention, and the use of said polymers overthe current use of hydroxy cellulose compounds.

The essential characteristics of an ideal wetting solution can besummarized as follows:

It should wet thoroughly and spread over the entire surface of the lens;

It should form a film which is sufficiently tenacious so that it willnot be washed away during the wearing period of the lens;

It should be so formulated that it can be placed directly into the eye,i.e. it should be non-irritating and non-sensitizing;

It should be a compound so that it will not leave a residue of film onthe lenses or the skin around the eye after drying;

It should have a cleaning and antiseptic action and should beself-preserving;

It should not interfere with immersion wetting by the lachrymal fluid;

It should have the proper degree of viscosity for efficient lubrication.

In accordance with the present invention, a contact lens solution madewhich has all of the above desirable attributes is made containing as aningredient a N-acetyl-D-glucosamine compound, (i.e. chitosan), sincethese polymers exhibit the necessary properties for use in contact lenssolutions.

As specific examples of ophthalmic solutions, the following examples aregiven only as an illustration:

EXAMPLES

Artificial tears consisting of a sterile solution of 1.8% to 3.4% of aD-glucosamine, 0.5% polysorbate 80 (polyoxyethylene(20) sorbitanmonooleate), in an isotonic solution preserved with 0.5% chlorobutanol.It is used to counteract dryness in the absence of natural tears or fromirritation due to excessive wearing of contact lenses, 2 or 3 drops areplaced in the eye several times a day.

Contact lens cleaning solution: Surfactant 3.5%, thimerosal 0.004%disodium edelate 0.2%, D-glucosamine 0.8%, distilled water. The cleaneris used to clean hard and gas permeable contact lenses. Soakingsolution: D-glucosamine 1.2%, thimerosal 0.001%, chlorhexidine 0.005%,disodium edelate 0.1%, isotonic solution of sodium chloride, sodiumborate, boric acid to ph 7.2 and water.

Anti-inflammatory ointment; polymyxin B sulfate 5,000 units/gr., zincbacitracin 400 units/gr., neomycin sulfate 5 mg/gr., hydrocortisone 10mg/gr., D-glucosamine 18.7%/gr., white petroleum remainder.

The D-glucosamines can also be used as carriers for all other ophthalmicpharmaceuticals, such as drugs which produce mydriasis and cyclopegis,and phenylephrine, adrenaline, cocaine, atropine, etc. The use ofglaucoma treatment agents can be combined with the D-glucosamine toincrease the viscosity and therapeutic effectiveness of the drugs suchas epinephrine.

The following examples are given to illustrate the methods of graftingonto chitin and chitosan, and in no way are to imply any limitations onthe invention.

EXAMPLE

A 26 oz bottle was charged with 10 gms CTC organics Chitin Flake (95.1%nonvolatile), and 190 gms deionized water. Nitrogen was bubbled throughthe mix for 30 minutes and the bottle was sealed overnight. A 0.1 Mcerium solution was prepared: 5.48 gms (NH₄)-₂ Ce(NO₃)₆ qs 0.25 N HNO₃to 100 ml total. A 12 ml quantity of cerium solution was added to thebottle, the bottle was flushed with nitrogen, sealed and agitated for 10minutes. The bottle was opened, 5 gms of methacrylic acid was added, thebottle was flushed with nitrogen, sealed, and tumbled 3 hours in a 35°C. polymerization oven to batch graft the acrylic acid to the Chitin.The bottle contents were washed into a weighed dish, evaporated in anair draft for two days, and dried in a vacuum oven to determine theyield. The Chitin and Chitosan flakes were also dried to determine thevolatile content. The % of monomer was calculated as follows:

% Monomer polymerized=Final dry weight-weight of dry basisChitosan/weight of monomer charged.

A similar procedure was followed for the methyl methacrylate graft,Chitosan and MMA were utilized: 10 gms CTC Organics Chitosan flake, 190gms deionized water, 12 ml 0.1 M Cerium Solution 5 gms R&H MethylMethacrylate. The % of monomer polymerized is as follows:Chitin-methacrylic acid 26.8. Insoluble in DMF, sodium/hydroxidesolution.

Chitosan-Methyl methacrylate 18.7, insoluble in dichloroethane, in 2%acetic acid, the polymer is largely soluble but a quantity of whitematerial slowly settles out. Castings were prepared by dissolvingChitosan (4% solids) and Croda Inc. Crotein SPC Collagen (8% solids) in2% acetic acid, mixing the solutions (50 Chitosan/50 Crotein solids) anddrying down at 60° C. with a 4 hour/100° C. post heating to encourageinteraction. Filtered Chitosan solution was used.

The above examples illustrate the process of utilizing ceric salts, suchas the ceric ammonium nitrate to initiate free radical graftingcopolymerization on chitin and chitosan.

These examples are merely a simplified illustration and are not to beunderstood as limiting the scope and underlying principles of this partof the invention in any way. Which is the utilization of D-glucosaminecompounds in all opthalmic preparations, either by themselves, or inconjunction with other chemicals, and known preparations and compounds.

The chitin derivatives contemplated for incorporation into opthalmicsolutions and ointments are also materials formed with pharmaceuticallyacceptable radicals and esters or salts with pharmaceutically acceptableacids. However, in certain opthalmic application of ointments andsolutions it may be preferred to use natural chitin or chitosan.

With some though it is evident that permutations and combinations amongthe various polymers and copolymers presented here can be found. It isalso apparent that changes and modifications may be made withoutdeparting from the invention in its broader aspects. The aim of theappended claims, therefore is to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed is:
 1. A polymeric composition formed from D-glucosamineor derivatives thereof selected from the group consisting ofN-acetyl-D-glucosamine, substituted N-acetyl-D-glucosamine, derivativesof N-acetyl-D-glucosamine and graft and block polymers ofN-acetyl-D-glucosamine, and a compound selected from the groupconsisting of a silicone, collagen, acrylonitrile, acrylamide,methacrylate acids and esters, alkylaminoalkyl methacrylate andhydroxyalkyl methacrylate and pyrrolidone and derivatives ofpyrrolidone.
 2. A composition according to claim 1 consisting of aD-glucosamine or derivative thereof and silicone.
 3. A compositionaccording to claim 1 consisting of a D-glucosamine or derivative thereofand collagen.
 4. A composition according to claim 1 consisting of aD-glucosamine or derivative thereof and acrylonitrile.
 5. A compositionaccording to claim 1 consisting of a D-glucosamine or derivative thereofand acrylamide.
 6. A composition according to claim 1 consisting of aD-glucosamine or derivative thereof and methacrylate acids and esters,alkylaminoalkyl methacrylate and hydroxyalkyl methacrylate.
 7. Acomposition according to claim 1 consisting of a D-glucosamine orderivative thereof and pyrrolidone or a derivative thereof.